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                  <p class="p_Heading1"><span class="f_Heading1">Communication Diagram</span></p>



  
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                <p class="p_BodyText"><span class="f_BodyText">One of four types of </span><span class="f_BodyText" style="font-style: italic;">Interaction</span><span class="f_BodyText"> diagram. (The other three are <a href="timingdiagram.htm">Timing Diagrams</a>, <a href="sequencediagram.htm">Sequence Diagrams</a> and <a href="interactionoverviewdiagram.htm">Interaction Overview Diagrams</a>.)</span></p>
<p class="p_BodyText"><span class="f_BodyText">A </span><span class="f_BodyText" style="font-style: italic;">Communication diagram</span><span class="f_BodyText"> shows the interactions between elements at run-time in much the same manner as a Sequence diagram. However, Communication diagrams are used to visualize inter-object relationships, while Sequence diagrams are more effective at visualizing processing over time.</span></p>
<p class="p_BodyText"><span class="f_BodyText">Communication diagrams employ ordered, labeled associations to illustrate processing. Numbering is important to indicate the order and nesting of processing. A numbering scheme could be:</span></p>
<p class="p_BodyText"><span class="f_BodyText">1</span><br>
<span class="f_BodyText">1.1</span><br>
<span class="f_BodyText">1.1.1</span><br>
<span class="f_BodyText">1.1.2</span><br>
<span class="f_BodyText">1.2, and so on.</span></p>
<p class="p_BodyText"><span class="f_BodyText">A new number segment begins for a new layer of processing, and would be equivalent to a method invocation.</span></p>
<p class="p_BodyText"><span class="f_BodyText" style="font-style: italic;">Robustness diagrams</span><span class="f_BodyText"> are simplified Communication diagrams, but can be created in any diagram type that supports <a href="boundary.htm">Boundary</a>, <a href="control.htm">Control</a> and <a href="entity.htm">Entity</a> elements. </span></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Example Diagram</span></p>
<p class="p_BodyText"><span class="f_BodyText">The example below illustrates a Communication diagram among cooperating object instances. Note the use of message levels to capture related flows, and the different <a href="communicationdiagramsincolo.htm">colors</a> of the <a href="message(communication).htm">messages</a>.</span></p>
<p class="p_TextIndentedL2"><img src="example%20of%20a%20communication%20diagram.png" width="820" height="515" border="0" alt="Example of a Communication Diagram"></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Toolbox Elements and Connectors</span></p>
<p class="p_BodyText"><span class="f_BodyText">Select Communication diagram elements and connectors from the </span><span class="f_UIControl"><a href="communicationgroup.htm">Communication</a></span><span class="f_BodyText"><a href="communicationgroup.htm"> pages</a> of the Enterprise Architect UML</span><span class="f_UIControl"> Toolbox</span><span class="f_BodyText" style="font-style: italic;">.</span></p>
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<td valign="bottom" width="955" bgcolor="#efeff7" style="width:955px; background-color:#efeff7;"><p class="p_TiporNote" style="border-top: none; border-right: none; border-left: none;"><span class="f_TiporNote">Tip:</span></p>
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<td width="955" bgcolor="#f7f7ff" style="width:955px; background-color:#f7f7ff;"><p class="p_TiporNoteText"><span class="f_TiporNoteText">Click on the following elements and connectors for more information.</span></p>
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<td valign="top" width="224" bgcolor="#e3e6ed" style="width:224px; background-color:#e3e6ed; border: solid 1px #000000;"><p class="p_Tableheader"><span class="f_Tableheader">Communication Diagram Elements</span></p>
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<td valign="top" width="230" bgcolor="#e3e6ed" style="width:230px; background-color:#e3e6ed; border: solid 1px #000000;"><p class="p_Tableheader"><span class="f_Tableheader">Communication Diagram Connectors</span></p>
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<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">OMG UML Specification</span></p>
<p class="p_BodyText"><span class="f_BodyText">The OMG UML specification (</span><span class="f_BodyText" style="font-style: italic;">UML Superstructure Specification, v2.1.1, p. 511</span><span class="f_BodyText">) states:</span></p>
<p class="p_OMGText"><span class="f_OMGText">Communication Diagrams focus on the interaction between Lifelines where the architecture of the internal structure and how this corresponds with the message passing is central. The sequencing of Messages is given through a sequence numbering scheme.</span></p>
<p class="p_OMGText"><span class="f_OMGText">Communication Diagrams correspond to simple Sequence Diagrams that use none of the structuring mechanisms such as InteractionUses and CombinedFragments. It is also assumed that message overtaking (i.e., the order of the receptions are different from the order of sending of a given set of messages) will not take place or is irrelevant.</span></p>
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<td valign="bottom" width="955" bgcolor="#efeff7" style="width:955px; background-color:#efeff7;"><p class="p_TiporNote" style="border-top: none; border-right: none; border-left: none;"><span class="f_TiporNote">Note:</span></p>
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<td width="955" bgcolor="#f7f7ff" style="width:955px; background-color:#f7f7ff;"><p class="p_TiporNoteText"><span class="f_TiporNoteText">Communication diagrams were known as Collaboration diagrams in UML 1.4.</span></p>
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